Thermal paste containment for semiconductor modules

ABSTRACT

A semiconductor module structure and a method of forming the semiconductor module structure are disclosed. The structure incorporates a die mounted on a substrate and covered by a lid. A thermal compound is disposed within a thermal gap between the die and the lid. A barrier around the periphery of the die extends between the lid and the substrate, contains the thermal compound, and flexes in response to expansion and contraction of both the substrate and the lid during cycling of the semiconductor module. More particularly, either the barrier is formed of a flexible material or has a flexible connection to the substrate and/or to the lid. The barrier effectively contains the thermal compound between the die and the lid and, thereby, provides acceptable and controlled coverage of the thermal compound over the die for heat removal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 11/755,019filed May 30, 2007, the complete disclosure of which, in its entirety,is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to a semiconductor module structure andmethod of forming the semiconductor module structure and, moreparticularly, to a thermal paste containment system incorporated into asemiconductor module structure and a method for forming the thermalpaste containment system within the semiconductor module.

2. Description of the Related Art

Many structures are known for removing or dissipating heat fromsemiconductor dies. In one structure a die is mounted on a substrate anda flat cooling plate or flat lid is placed over a die. The gap betweenthe die and the lid are filled in with a thermal compound (i.e., thermalgrease, thermal paste, thermal gel, etc.), which promotes heatconduction between the lid and the die. Controlling the coverage of thethermal paste over the die to ensure that the gap is filled in iscritical for heat removal. Thermal cycling of the semiconductor modulecan result in the expansion and contraction of the lid and substrate.This expansion and contraction can result in pumping of the thermalcompound such that the thermal compound moves out of the interfacebetween the die and the lid, leaving air pockets and reducing effectiveheat removal. This disclosure presents a method and structure forcontaining the thermal compound between the die and lid to limit theeffects of thermal compound pumping.

SUMMARY OF THE INVENTION

This disclosure presents a semiconductor module with a thermal compoundcontainment system and a method of forming the semiconductor module.Embodiments of the semiconductor module comprise a die mounted on asubstrate and covered by a lid. A thermal compound is disposed betweenthe die and the lid such that it covers the die and fills in any gapsbetween the die and the lid. A barrier is positioned adjacent to theperiphery of the die and extends vertically between the substrate andthe lid in order to contain the thermal compound. The lid is planar andextends horizontally over the die and beyond the barrier. The lid canfurther comprise an outer rim that projects towards the substrate and issealed thereto (e.g., by a thermosetting sealant). The barrier isparticularly configured to flex in response to expansion and contractionof the substrate and the lid in response to thermal cycling.Specifically, the barrier can either comprise a fully flexible materialor a flexible connection between the body of the barrier and thesubstrate (i.e., first connection) and/or the lid (i.e., secondconnection). In either structural embodiment the barrier can compriseone or more openings that allow excess thermal compound to escape thethermal gap between the die and lid during the manufacturing process.

More particularly, in one embodiment of the structure of the invention,the barrier can comprise a flexible polymer material, such as a curedb-stage epoxy resin. This flexible barrier can adhere directly to boththe substrate and the lid in order to form the first connection and thesecond connection. Alternatively, this flexible barrier can adheredirectly only to the substrate. If the barrier adheres directly only tothe substrate, then the lid can comprise a plurality of extensions toconnect the lid to the barrier. For example, the plurality of extensionscan project away from the lid towards the substrate and can align overthe barrier. The extensions can be adapted to penetrate and to remainfixed to the barrier when the lid covers the die.

In another embodiment of the structure of the invention, the body of thebarrier can comprise a rigid material (e.g., a metal or a plasticmaterial). In order to ensure that the barrier is adapted to flex inresponse to expansion and contraction of the substrate and the lid, thefirst connection and/or the second connection comprises a flexibleconnection (e.g., a connection formed of a cured material such as anelastomer or a b-stage epoxy resin). For example, a groove can be formedin the bottom surface of the lid and can be adapted for receiving thebarrier. When the lid covers the die, a flexible connection between thebody of the barrier and the groove can be formed with a cured elastomeror a cured b-stage epoxy resin that adheres the barrier within thegroove. In another example, the body of the barrier can comprise rigidmaterial fixedly attached or integral to the lid (e.g., a metal barriermachined into the lid). When the lid covers the die, a flexibleconnection between the body of the barrier and the substrate can beformed with a cured material, such as an elastomer or a b-stage epoxyresin. In yet another example, the body of the barrier can be formed byattaching a rigid material (e.g., metal or plastic) onto the substrateusing a cured material, such as an elastomer or a cured b-stage epoxyresin, to form a flexible connection. The lid can comprise a pluralityof extensions that project away from the lid and aligned above thebarrier. The plurality of extensions can be adapted to penetrate andremain fixed to the rigid material forming the barrier, as the lidcovers the die.

Embodiments of the method of forming a semiconductor module having athermal compound containment system comprise forming a barrier that isparticularly adapted to flex in response to expansion and contraction ofthe substrate and the lid, either because the barrier is formed of aflexible material or because the barrier comprises a flexible connectionto the substrate (i.e., first connection) and/or the lid (i.e., secondconnection). In one embodiment of the method the barrier is formed of aflexible material. This method comprises mounting a die on a top surfaceof a substrate. A lid is formed that is configured to cover the die andto extend beyond the periphery of the die. The lid can further be formedwith an outer rim that extends towards the substrate and is sealedthereto. A flexible barrier is formed such that when the lid covers thedie, the barrier is positioned adjacent the periphery of the die andextends vertically between the substrate and the lid to create a thermalgap. The flexible barrier comprises a material adapted to flex inresponse to expansion and contraction of the substrate and the lid. Athermal compound is disposed within the thermal gap between the lid andthe die. The process of disposing the thermal compound within thethermal gap can comprise before covering the die with the lid,depositing the thermal compound on the die and/or the lid such that whenthe lid covers the die the thermal compound is disposed within thethermal gap. The flexible barrier is configured to prevent the thermalcompound from flowing outside the thermal gap. Forming the flexiblebarrier comprises patterning the flexible barrier with at least oneopening to allow air and/or excess thermal compound to escape thethermal gap during the process of forming the semiconductor module.Forming the flexible barrier can comprise depositing a curable material(i.e., a curable polymer such as an elastomer or a b-stage epoxy resin)on the lid and/or the substrate such that when the lid covers the die,the curable material extends between the substrate and the lid. Thematerial is cured in order to form the flexible barrier and to adherethe flexible barrier to the lid and the substrate. Alternatively, theflexible barrier can be formed by depositing a curable material (i.e., acurable polymer such as an elastomer or an epoxy resin) on the substratesuch that when the lid covers the die, the barrier extends from thesubstrate towards the lid. The material is cured to form the flexiblebarrier and to adhere the flexible barrier to the substrate. Theflexible barrier can be connected and sealed to the bottom surface ofthe lid (i.e., surface covering the die) by a plurality of extensionsthat, when the lid covers the die, project from the bottom surface ofthe lid towards the substrate and are aligned above the flexiblebarrier. The plurality of extensions provides a contact area forconnecting the barrier to the lid in order to form a complete barrierstructure. The extensions can further be configured to penetrate theflexible barrier and to remain fixed to the flexible barrier when thelid covers the die.

In another embodiment of the method, the flexible barrier is formed byforming a body of the barrier with a flexible connection to thesubstrate (i.e., first connection) and/or the lid (i.e., secondconnection). The method comprises mounting a die on a top surface of asubstrate. A lid is formed that is configured to cover the die and toextend beyond the periphery of the die. The lid can also be formed withan outer rim that projects toward the substrate and is sealed thereto.The body of the barrier is formed with a rigid material (e.g., metal orplastic) that is configured to be positioned adjacent the periphery ofthe die and to extend vertically between the substrate and the lid whenthe lid covers the die, thus, creating a thermal gap. The body of thebarrier is flexibly connected to the lid and/or the substrate. Theflexible connection is adapted to allow the thermal gap to flex inresponse to expansion and contraction of the substrate and the lid. Athermal compound is disposed within the thermal gap between the lid andthe die. Again, the process of disposing the thermal compound within thethermal gap can comprise before covering the die with the lid,depositing the thermal compound on the die and/or the lid such that whenthe lid covers the die the thermal compound is disposed within thethermal gap. The barrier is configured to prevent the thermal compoundfrom flowing outside the thermal gap. As with the previously describedembodiment, forming the barrier can comprise patterning the barrier withat least one opening to allow air and excess thermal compound to escapethe thermal gap during the process of forming the semiconductor module.The flexible connection may be between the body of the barrier and thelid. For example, the body of the barrier can be formed by positioning arigid material (e.g., a metal or plastic) on the substrate. Theconnection between the body of the barrier and the substrate may or maynot be flexible. The lid is formed with a groove, adapted for receivinga top of the body of the barrier. A curable material (i.e., a curablepolymer such as an elastomer or an epoxy resin) can be deposited ontothe body of the barrier and/or in the groove of the lid. When the lidcovers the die, the top of the body of the barrier is received by thegroove. The material is cured such that the body of the barrier isadhered to the groove in the lid and a flexible connection is created.Alternatively, the flexible connection may be between the body of thebarrier and the substrate with the connection between the body of thebarrier and the lid optionally flexible. For example, the body of thebarrier may be integrally formed with the lid, such as a metal body ofthe barrier machined into a metal lid. A curable material (i.e., acurable polymer), deposited on the bottom of the body of the barrier oron the substrate adjacent to the periphery of the die, is used toflexibly connect the body of the barrier to the substrate when the lidcovers the die. In another example, the body of the barrier may beformed on the lid by attaching the rigid material to the lid with anadhesive, connector, etc. In this example, a curable material that isdeposited on the bottom of the body of the barrier or on the substrateadjacent to the periphery of the die would also be used to flexiblyconnect the body of the barrier to the lid when the lid covers the die.In another example, the body of the barrier may be formed on thesubstrate by attaching the rigid material to the substrate with acurable material (i.e., a curable polymer) to form the flexibleconnection. The lid in this example is formed with a plurality ofextensions configured to project from the lid towards the substrate andto align over the body of the barrier, when the lid covers the die. Theextensions provide a contact area for connecting the body of the barrierto the lid in order to form a complete barrier structure. The extensionscan further be configured to penetrate the barrier and to remain fixedthereto.

These, and other, aspects and objects of the present invention will bebetter appreciated and understood when considered in conjunction withthe following description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the present invention and numerous specificdetails thereof, is given by way of illustration and not of limitation.Many changes and modifications may be made within the scope of thepresent invention without departing from the spirit thereof, and theinvention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detaileddescription with reference to the drawings, in which:

FIG. 1 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 2 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 3 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 4 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 5 is a schematic illustration of a completed semiconductor moduleof the present invention;

FIG. 6 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 7 is a schematic illustration of a completed semiconductor moduleof the present invention;

FIG. 8 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 9 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 10 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 11 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 12 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 13 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 14 is a schematic illustration of a completed semiconductor moduleof the present invention;

FIG. 15 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 16 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 17 is a schematic illustration of a completed semiconductor moduleof the present invention;

FIG. 18 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 19 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 20 is a schematic illustration of a partially completedsemiconductor module of the present invention;

FIG. 21 is a schematic illustration of a completed semiconductor moduleof the present invention;

FIG. 22 is a schematic flow diagram illustrating an embodiment of themethod of the invention;

FIG. 23 is a schematic flow diagram illustrating another embodiment ofthe method of the invention;

FIG. 24 is a schematic flow diagram illustrating another embodiment ofthe method of the invention;

FIGS. 25-27 are schematic flow diagrams illustrating exemplary steps forcompleting method processes 2404, 2405 and 2406 of the embodiment of themethod illustrated in FIG. 24; and

FIGS. 28-30 are schematic illustrations of exemplary barrier patternsreferred to in method processes 2204, 2304 and 2404 of the embodimentsof the method illustrated in FIGS. 22-24, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.Descriptions of well-known components and processing techniques areomitted so as to not unnecessarily obscure the present invention. Theexamples used herein are intended merely to facilitate an understandingof ways in which the invention may be practiced and to further enablethose of skill in the art to practice the invention. Accordingly, theexamples should not be construed as limiting the scope of the invention.

As stated above, controlling the coverage of a thermal compound (i.e.,thermal paste, gel, grease, etc.) over the die to ensure that gaps arefilled in between the die and lid throughout the life of the applicationis critical for heat removal. Temperature cycling of the semiconductormodule can result in the expansion and contraction of the lid andsubstrate. This expansion and contraction can result in changes in thegap between the die and the lid causing pumping of the thermal compoundsuch that the thermal compound moves away from the interface between thedie and the lid. U.S. Pat. No. 5,706,171 to Edwards et al. issued onJan. 6, 1998; U.S. Pat. No. 5,891,755 issued to Edwards et al. on Apr.6, 1999; and, U.S. Pat. No. 6,794,749 issued to Akram on Sep. 21, 2004,each of which are incorporated herein by reference, disclosesemiconductor chip package structures incorporating thermal compounds todissipate heat as well as a means for containing the thermal compounds.The disclosed structures are rigid to prevent any movement of thethermal paste. However, manufacturing such structures may be costly andinefficient. This disclosure presents an alternative structure forcontaining a thermal compound between the die and lid of a semiconductormodule in order to limit the effects of thermal compound pumping and amethod for manufacturing the structure.

More particularly, this disclosure presents a semiconductor module thathas a thermal compound containment system and a method of forming thesemiconductor module. Referring to FIG. 1, embodiments of thesemiconductor module of the present invention each comprise a die 10,having an outer periphery 9. The die 10 is mounted (e.g., by solderjoints 11) on a substrate 12. Referring to the exemplary completedsemiconductor module structures (500, 700, 1100, 1400, 1700 and 2100) ofFIGS. 5, 7, 11, 14, 17, and 21, respectively, each structural embodimentfurther comprises a lid (513, 713, 1113, 1413, 1713 and 2113) whichcovers the die 10. A thermal compound (515, 715, 1115, 1415, 1715 and2115) is disposed between the die 10 and the lid (513, 713, 1113, 1413,1713 and 2113) such that it covers the die 10 and fills in the thermalgap between the die 10 and the lid (513, 713, 1113, 1413, 1713 and2113). A barrier (514, 714, 1114, 1414, 1714 and 2114) is positionedadjacent the periphery 9 of the die 10, and thereby, around the thermalcompound (515, 715, 1115, 1415, 1715 and 2115). The barrier (514, 714,1114, 1414, 1714 and 2114) extends vertically between the substrate 12and the lid (513, 713, 1113, 1413, 1713 and 2113) defining the thermalgap (516, 716, 1116, 1416, 1716 and 2116). The lid (513, 713, 1113,1413, 1713 and 2113) is planar and extends horizontally over the thermalcompound (515, 715, 1115, 1415, 1715 and 2115) and beyond the barrier(514, 714, 1114, 1414, 1714 and 2114). The lid (513, 713, 1113, 1413,1713 and 2113) can further comprise an outer rim (517, 717, 1117, 1417,1817 and 2117) that projects towards the substrate 12 and is sealedthereto (e.g., by a flexible sealant (518, 718, 1118, 1418, 1718 and2118). The barrier (514, 714, 1114, 1414, 1714 and 2114) also comprisesa first connection (521, 721, 1121, 1421, 1721 and 2121), that connectsthe barrier (514, 714, 1114, 1414, 1714 and 2114) to the substrate 12and a second connection (522, 722, 1122, 1422, 1722 and 2122) thatconnects the barrier (514, 714, 1114, 1414, 1714 and 2114) to the lid(513, 713, 1113, 1413, 1713 and 2113). The barrier (514, 714, 1114,1414, 1714 and 2114) is adapted to contain the thermal compound (515,715, 1115, 1415, 1715 and 2115) that is located within the thermal gap(516, 716, 1116, 1416, 1716 and 2116). The barrier (514, 714, 1114,1414, 1714 and 2114) is also particularly configured such that it flexesin response to expansion and contraction of the substrate 12 and the lid(513, 713, 1113, 1413, 1713 and 2113) during thermal cycling of thesemiconductor module, Specifically, in one structural embodiment thebarrier flexes because it comprises a flexible material (e.g., barriers514 and 714 of FIGS. 5 and 7, respectively). In another structuralembodiment the barrier flexes because of a flexible connection betweenthe body of the barrier and the substrate (i.e., a first connection)and/or between the body of the barrier and the lid (i.e., a secondconnection). For example, see barriers 1114, 1414, 1714 and 2114 ofFIGS. 11, 14, 17 and 21, respectively.

FIGS. 5 and 7 are exemplary illustrations of structures 500 and 700 inwhich the barrier 514, 714 comprises a flexible material (e.g., a curedmaterial such as a thermosetting elastomer or b-stage epoxy resin).Referring to FIG. 5, in one embodiment the flexible barrier 514 canadhere directly to both the substrate 12 and the lid 513 in order toform the first connection 521 and the second connection 522,respectively. Note that the lid 513 (in this structural embodiment andin any of the other structural embodiments discussed below) may beformed with a pedestal 528 (see FIG. 2) configured to be positioned onthe thermal compound 515 (e.g., see the thermal compound 515 depositedon the pedestal 528 of FIG. 4). Alternatively, referring to FIG. 7, aflexible barrier 714 (e.g., a cured material such as a thermosettingelastomer or b-stage epoxy resin) can adhere directly to the substrate12 and be otherwise connected to the lid 713. For example, the lid 713can comprise a plurality of extensions 719 that provide a barriercontact area for connecting the lid 713 to the barrier 714 in order toform a complete barrier structure (i.e., second connection 722). Theextensions 719 can project away from the lid 713 towards the substrate12 and can be aligned over the barrier 714, which the lid 713 covers thedie 10. The extensions 719 can be adapted to penetrate and to remainfixed to the barrier 714. The extensions 719 can comprise blades withvarious features.

FIGS. 11, 14, 17, and 21 are exemplary illustrations of structures(1100, 1400, 1700 and 2100) in which the barrier comprises a flexibleconnection to the substrate (i.e., first connection (1121, 1421, 1721and 2121)) and/or a flexible connection to the lid (i.e., secondconnection (1122, 1422, 1722 and 2122)). The barrier (1114, 1414, 1714and 2114) of these embodiments can comprise a rigid material (e.g., ametal or a plastic material). In order to ensure that the barrier (1114,1414, 1714 and 2114) is adapted to flex in response to expansion andcontraction of the substrate 12 and the lid (1113, 1413, 1713 and 2113),the first connection (e.g., 1421, 1721, 2121 and possibly 1121 of FIGS.14, 17, 21 and 11, respectively) or the second connection (e.g., 1122and possibly 1422 of FIGS. 11 and 14, respectively) comprise a flexibleconnection (e.g., a connection formed of a curable material (i.e., acurable polymer) 1126, 1426, 1726, and 2126, such as an elastomer orb-stage epoxy resin). For example, referring to structure 1100 of FIG.11, a groove 1125 can be formed in the lid 1113 and can be adapted forreceiving the barrier 1114 when the lid 1113 covers the die 10. Thebarrier 1114 is formed on the substrate 12. The first connection 1121may be flexible (e.g., by using a thermosetting elastomer or b-stageepoxy resin) or the first connection 1121 may be rigid. A flexiblesecond connection 1122 between the body of the barrier 1114 and thegroove 1125 can be formed with a curable material (i.e., a curablepolymer) 1126 deposited into the groove 1125 and/or onto the barrier1114. Once the lid 1113 covers the die 10 and the thermal compound 1115is disposed between the lid 1113 and the die 10, the curable material1126 is cured in order to flexibly adhere the barrier 1114 within thegroove 1125. Alternatively, referring to structures 1400 of FIGS. 14 and1700 of FIG. 17, the barrier 1414, 1714 can comprise a rigid material(e.g., metal or plastic) formed on the lid 1413, 1713 and may beconnected (either flexibly or rigidly) to the lid, as illustrated inFIG. 14. The barrier may also be formed integral with the lid, asillustrated by the metal barrier 1714 machined into the lid 1713. Whenthe lid 1413, 1713 covers the die 10, a flexible first connection 1421,1721 can be formed with a curable material 1426, 1726 (e.g., athermosetting elastomer or an epoxy resin) and curing the curablematerial. Alternatively, referring to structure 2100 of FIG. 21, thebarrier 2114 (e.g., metal or plastic) can be formed on the substrate 12with a flexible first connection 2121 by connecting the body of thebarrier 2114 to the substrate 12 with a curable material 2126. The lid2113 can comprise a plurality of extensions 2119 that project away fromthe lid 2113 towards the substrate 12 and can be aligned above thebarrier 2114 to provide a barrier contact area for connecting the lid2113 to the barrier 2114. The plurality of extensions 2119 can beadapted to penetrate and remain fixed to the rigid barrier 2114 when thelid 2113 covers the die 10. The extensions 2119 can comprise blades withvarious features.

Embodiments of the method of forming a semiconductor module having athermal compound containment system comprise forming a barrier that isparticularly adapted to flex in response to expansion and contraction ofthe substrate and the lid, either because the barrier is formed of aflexible material or because the barrier comprises a flexible connectionto the substrate (i.e., first connection) and/or the lid (i.e., secondconnection). The flow diagrams of FIGS. 22 and 23 illustrate embodimentsof the method of forming structures of the present invention thatincorporate a barrier comprising a flexible material, as illustrated inexemplary structures 500 and 700 of FIGS. 5 and 7. The flow diagram ofFIG. 25 illustrates an embodiment of the method of forming structures ofthe present invention that incorporate a barrier with a body having aflexible connection to the substrate and/or the lid, as illustrated instructure 1100, 1400, 1700, and 2100 of FIGS. 11, 14, 17, and 21. All ofthese methods comprise mounting a die 10, having a periphery 9, on a topsurface of a substrate 12, as illustrated in FIG. 1 (2201, 2301, and2401). A lid is formed that is configured to cover the die 10 and toextend beyond the periphery 9 of the die 10 (2202, 2302, and 2402).

Referring to the flow diagram of FIG. 22 and the structure 500 of FIG.5, the die 10 is mounted on the substrate 12 (2201, see FIG. 1) and thelid 513 is formed (2202, see FIG. 2). The lid can be formed with apedestal 528, although not required, in an area corresponding to the die10 for positioning adjacent the thermal compound 515. The lid 513 canfurther be formed with an outer rim 517 that extends towards thesubstrate 12 and is sealed thereto by sealant 518 at process 2210. Aflexible barrier 514 can be formed on the lid 513 and/or the substrate12 such that when the lid covers the die (at process 2208), the flexiblebarrier 514 is positioned adjacent the periphery 9 of the die 10 andextends vertically between the substrate 12 and the lid 513 to create athermal gap 516 (2204, see FIG. 3). The flexible barrier 514 comprises amaterial adapted to flex in response to expansion and contraction of thesubstrate 12 and the lid 513. During the process of forming the flexiblebarrier (2204), the barrier 514 can be patterned (see discussionregarding FIGS. 28-30 below) with at least one opening to allow airand/or excess thermal compound 515 to escape the thermal gap 516 duringthe process of forming the semiconductor module. The flexible barrier514 can be formed by depositing a curable material (e.g., a polymer suchas a b-stage epoxy resin which can be dispensed or applied as a b-stagedecal) onto the substrate 12 or the lid 513. A thermal compound 515 isdeposited on the die and/or the lid such that when the lid covers thedie (at process 2208) the thermal compound is disposed within thethermal gap (as illustrated in FIG. 4) (2206). The lid 513 is placedover the die 10 so that the barrier 514 extends between the substrate 12and the lid 513 to form the thermal gap 516 (2206). An outer rim 517 ofthe lid 513 can be sealed to the substrate 12 by sealant 518 (2210). Theflexible barrier 514 is configured to prevent the thermal compound 515from flowing outside the thermal gap 516. The curable materials (e.g.,barrier 514 and sealant 518) should be cured (2214) (e.g., in anapproximately 125-150 degree Celcius range for approximately 1-2 hours).Curing the barrier 514 simultaneously sets the flexible barrier andadheres the flexible barrier to the lid 514 and the substrate 12.Lastly, vents in the lid 513 that allow air to escape during theencapping process should be plugged (e.g., vent 530 plugged with plug531) (2216). For example, to form the plug 531 an elastomer mechanicalpin made of a fluorocarbon material may be inserted into the vent 530followed applying a non-thermal sealant such as a UV adhesive.

Alternatively, referring to the flow diagram of FIG. 23 and thestructure 700 of FIG. 7, the die 10 is mounted on the substrate 12(2301, see FIG. 1) and the lid 713 is formed (2302, see FIG. 6). The lid713 can be formed with a pedestal 728, although not required, in an areacorresponding to the die 10 for positioning adjacent the thermalcompound 715 (see FIG. 6). More, particularly, the lid 713 of FIG. 7 isformed with a plurality of extensions 719 (see FIG. 6) such that theextensions 719 project from the bottom surface of the lid 713, arealigned above the flexible barrier 714 when the lid 714 covers the die10 (at process 2306). Theses extensions 719 provide a barrier contactarea for connecting the lid 713 to the barrier 714 in order to form acomplete barrier structure. The plurality of extensions 719 can beconfigured to penetrate the flexible barrier 714 and to remain fixed tothe flexible barrier 714 upon covering the die 10 with the lid 714. Theextensions 719 can comprise blades with various features. A flexiblebarrier 714 can be formed on the substrate 12 such that when the lid 713covers the die (at process 2308), the flexible barrier 714 is positionedadjacent the periphery 9 of the die 10 and extends vertically betweenthe substrate 12 and the lid 713 to create a thermal gap 716 (2304). Theflexible barrier 714 comprises a material adapted to flex in response toexpansion and contraction of the substrate 12 and the lid 713. Theflexible barrier 714 can be formed by depositing a curable material(e.g., a polymer such as a b-stage epoxy resin which can be dispensed orapplied as a b-stage decal) onto the substrate. As the flexible barrier714 is deposited, it can be patterned (see discussion regarding FIGS.28-30 below) with at least one opening to allow air and/or excessthermal compound 715 to escape the thermal gap 716 during the process offorming the semiconductor module (2304 a). The thermal compound 715 isdeposited on the die and/or the lid such that when the lid covers thedie (at process 2308) the thermal compound is disposed within thethermal gap (2306). The lid 713 is placed over the die 10 so that theextensions 719 penetrate the barrier 714 in order to form the thermalgap 716 (2308). An outer rim 717 of the lid 713 can be sealed to thesubstrate 12 by sealant 718 (2310). The flexible barrier 714 isconfigured to prevent the thermal compound 715 from flowing outside thethermal gap 716. The curable materials (e.g., barrier 714 and sealant718) should be cured (2314) (e.g., in an approximately 125-150 degreeCelcius range for approximately 1-2 hours). Curing the barrier 714simultaneously sets the flexible barrier 714 and adheres the flexiblebarrier 714 the substrate 12. Lastly, vents in the lid 713 that allowair to escape during the encapping process should be plugged (e.g., vent730 plugged with plug 731) (2316). For example, to form the plug 731 anelastomer mechanical pin made of a fluorocarbon material may be insertedinto the vent 730 followed by applying non-thermal sealant such as a UVadhesive.

Referring to the flow diagram of FIG. 24 and structures 1100, 1400,1700, and 2100 of FIGS. 11, 14, 17, and 21, respectively, the die 10 ismounted on the substrate 12 (2401, see FIG. 1) and the lid 1113 (seeFIG. 8), 1413 (see FIG. 12), 1713 (see FIG. 15), 2113 (see FIG. 18) isformed (2402). The lid 1113, 1413, 1713, 2113 is formed such that itwill cover the die 10 and extend beyond the periphery 9 of the die 10.The lid 1113, 1413, 1713, 2113 can also be formed with an outer rim1117, 1417, 1717, 2117 that projects toward the substrate 12 and issealed thereto by a sealant 1118, 1418, 1718, 2118 (at process 2408). Abarrier is formed on the lid or the substrate such that when the lidcovers the die the barrier is positioned adjacent the periphery of thedie and will extend vertically between the substrate and the lid (2404).As the barrier is formed (2404), it can be patterned (see discussionregarding FIGS. 28-30 below) with at least one opening to allow airand/or excess thermal compound to escape the thermal gap during theprocess of forming the semiconductor module. The barrier can be formedof a rigid material (e.g., metal or plastic) that is either integrallyformed with or attached to the substrate or the lid. The barrier isconfigured to prevent a thermal compound from flowing outside of thethermal gap created when the lid covers the die (at process 2406). Thebody of the barrier can be flexibly connected to the lid and/or thesubstrate (2407). The flexible connection is adapted to allow thethermal gap to flex in response to expansion and contraction of thesubstrate and the lid. A thermal compound is disposed within the thermalgap (2405). As discussed above with regard to other embodiments of themethod, the thermal compound is deposited onto the die (see FIGS. 13 and20) and/or onto the lid (see FIG. 16) such that when the lid covers thedie at process 2406 the thermal compound is disposed within the thermalgap. As the lid covers the die at process 2406, a rim of the lid can besealed to the substrate (2408). The curable materials (i.e., curablepolymers) 1126, 1426, 1726, 2126 used to flexibly connect the body ofthe barrier to the lid and/or the substrate, as well as the sealant,should be cured (2412) (e.g., in an approximately 125-150 degree Celciusrange for approximately 1-2 hours). Lastly, vents in the lid should beplugged (e.g., vents 1130, 1133 plugged with plugs 1131, 1134 (see FIG.11); vent 1430 plugged with plug 1431 (see FIG. 14); vent 1730 pluggedwith plug 1731 (see FIG. 17); and vent 2130 plugged with plug 2131 (seeFIG. 21)) (2414). For example, as mentioned previously vent plugs may beformed by inserting an elastomer mechanical pin made of a fluorocarbonmaterial into a vent, followed by applying a non-thermal sealant such asa UV.

Referring to the flow diagrams of FIGS. 25-28, processes 2402-2407 aredescribed in greater detail depending upon the structural embodiment.For example, referring to FIG. 25 and the structure 1100 of FIG. 11, aflexible connection is formed between the body of the barrier 1114 andthe lid 1113 (i.e., second connection 1122). The barrier 1114 is formedby forming a metal or plastic barrier on the substrate 12 (2504, seeFIG. 9). The first connection 1121 between the metal or plastic barrier1114 and the substrate 12 may or may not be flexible. The lid 1113 isformed with a groove 1125, adapted for receiving a top of the barrier1114 (2502, see FIG. 8). The body of the barrier 1114 is flexiblyconnected to the lid by a curable material (i.e., a curable polymer)1126 (e.g., a thermosetting elastomer or a thermosetting b-stage epoxyresin) deposited on the top of the barrier 1114 (see FIG. 10) and/orinto the groove 1125 (2506, see FIG. 11). When the lid 1113 covers thedie 10, the top of the barrier 1114 is received by the groove 1125(2505, see FIG. 11) and the curable material 1126 flexibly adheres thebarrier 1114 to the groove 1125.

Referring to the structures 1400, 1700 and 2100 of FIGS. 14, 17 and 21,respectively, the flexible connection may be formed between the body ofthe barrier 1414, 1714, 2114 and the substrate 12 (i.e., firstconnection 1421, 1721, 2121). The second connection 1422, 1722, 2122between the body of the barrier 1414, 1714, 2114 and the lid 1413, 1713,2113 may or may not be flexible. For example, referring to FIG. 7, thebarrier 1717 may be integrally formed with the lid 1713 such as a metalbarrier machined into a metal lid. Alternatively, referring to FIG. 21,the barrier 2114 may be connected to the lid 2113 by a plurality ofextensions 2119.

Referring particularly to the flow diagram of FIG. 26 and to structures1400 and 1700 of FIGS. 14 and 17, respectively, a rigid barrier 1414,1714 (e.g., metal or plastic) is formed on the lid 1413, 1713 (2604) Thebody of the barrier 1414, 1714 is flexibly connected to the substrate 12by depositing a curable material (i.e., a curable polymer) 1426, 1726(e.g., a thermosetting elastomer or a thermosetting b-stage epoxy resin)onto the barrier 1414, 1714 and/or onto the substrate adjacent theperiphery 9 of the die 10 (2606, see FIG. 13). The die 10 is thencovered with the lid 1413, 1713 so that the barrier 1414, 1714 isconnected to the substrate 12 by the curable material 1426, 1726 (2605,see FIGS. 14 and 17).

Referring particularly to the flow diagram of FIG. 27 and to thestructure 2100 of FIG. 21, in this embodiment a lid 2113 is formed witha plurality of extensions 2119 (2702, see FIG. 18). The extensions 2119can project from the bottom surface of the lid 2113 such that when thelid 2113 is placed over the die 10, the extensions 719 project towardsthe substrate and are aligned over the barrier 2114. The extensions 2119provide a barrier contact area for connecting the lid 2113 to thebarrier 2114 in order to form a complete barrier structure. Theextensions 2119 can be configured to penetrate the barrier 2114 and toremain fixed thereto as the lid 2113 covers the die 10. The extensions2119 can comprise blades with various features. Then, a curable material2126 (e.g., a thermosetting elastomer or a thermosetting b-stage epoxyresin) is deposited to on the substrate 12 adjacent the periphery 9 ofthe die 10 (2706) and the rigid barrier 2114 is placed in the curablematerial 1126 (2704, see FIG. 19). As the lid 2113 covers the die 10(2705), the extensions 2119 penetrate and remain fixed to the barrier2114.

As mentioned above, FIGS. 28-30 illustrate exemplary barrier 14patterns. These barrier 14 patterns are only exemplary and should not beviewed as limiting. These patterns may be used in method embodiments inwhich the barrier 14 is formed either on the substrate or on the lid.FIG. 28 illustrates a barrier 14 pattern with two opposing openings 35which will allow air and small amounts of excess thermal compound toescape the thermal gap as it is being filled. FIG. 29 illustratesanother barrier pattern in which a second barrier 14.2 surrounds a firstbarrier 14.1. Each barrier 14.1, 14.2 is configured with opposingopenings 35.1 and 35.2 that are offset by 45 degrees to create a longpath for the thermal compound to travel during the process of formingthe semiconductor module. FIG. 30 illustrates a barrier 14 comprised offour walls 14 a-d with openings 35 a-d in each corner. Note that if thefour-wall 14 a-b pattern of FIG. 30 is used, the barrier 14 may beformed on the lid, the substrate or divided and formed on both the lidand the substrate.

Thus, the present invention discloses a semiconductor module and amethod of forming the semiconductor module. The semiconductor module isconfigured to contain a thermal compound within a thermal gap between adie and a lid in order to ensure effective heat removal. Thesemiconductor module comprises a die mounted on a substrate andencapsulated by a lid. The semiconductor module further incorporates abarrier formed around the die between the substrate and a lid. Thethermal compound is enclosed within the barrier. The barrier isparticularly configured to flex in response to expansion and contractionof both the substrate and the lid during cycling of the semiconductormodule, and thus, to accommodate for thermal compound pumping. Thebarrier comprises either a fully flexible material or a flexibleconnection to the substrate and/or to the lid. The disclosedsemiconductor module effectively contains the thermal compound withinthe barrier between the die and the lid and, thereby, providesacceptable and controlled coverage of the thermal compound over the diefor heat removal. While the invention has been described in terms ofembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims.

1. A method of forming a semiconductor module, said method comprising:mounting a die, having a periphery, on a substrate; covering said diewith a planar lid having an outer rim such that, after said covering ofsaid die with said lid, said lid extends horizontally beyond saidperiphery of said die and said outer rim contacts said substrate so asto ensure that a bottom surface of said lid remains separated from a topsurface of said die by a gap; before said covering of said die with saidlid, depositing a thermal compound on at least one of said top surfaceof said die and a corresponding portion of said bottom surface of saidlid such that, after said covering of said die with said lid, saidthermal compound fills said gap without extending laterally beyond saidperiphery of said die; and forming a barrier such that, when said lidcovers said die, said barrier extends vertically between said lid andsaid substrate, is positioned laterally between said outer rim and saiddie and surrounds and is immediately adjacent to said periphery of saiddie so as to contain said thermal compound within said gap, said formingof said barrier further comprising: selecting a polymer material;depositing said polymer material on at least one of said lid and saidsubstrate such that, when said lid covers said die, said polymermaterial extends between and contacts both said substrate and said lid;and curing said polymer material to form said barrier such that saidbarrier comprises a single layer of flexible cured polymer that adheresdirectly to both said lid and said substrate, said selecting, saiddepositing and said curing being performed such that said barrier flexesin response to expansion and contraction of said substrate and said lidduring temperature cycling of said semiconductor module.
 2. The methodof claim 1, said forming of said barrier further comprising patterningsaid barrier with a plurality of discrete sections with openings betweensaid discrete sections to allow air and excess thermal compound toescape said barrier into a space between said barrier and said outer rimduring said process of forming said semiconductor module.
 3. The methodof claim 1, said polymer material comprising a b-stage thermosettingmaterial.
 4. The method of claim 1, further comprising forming said lidsuch that said lid comprises a pedestal on said corresponding portion ofsaid bottom surface and adapted to receive said thermal compound.
 5. Themethod of claim 4, further comprising forming said lid such that saidlid comprises vent holes; and after said forming of said semiconductormodule, plugging said vent holes in said lid.
 6. A method of forming asemiconductor module, said method comprising: mounting a die, having aperiphery, on a substrate; covering said die with a planar lid having anouter rim such that, after said covering of said die with said lid, saidlid extends horizontally beyond said periphery of said die and saidouter rim contacts said substrate so as to ensure that a bottom surfaceof said lid remains separated from a top surface of said die by a gap;before said covering of said die with said lid, depositing a thermalcompound on at least one of said top surface of said die and acorresponding portion of said bottom surface of said lid such that,after said covering of said die with said lid, said thermal compoundfills said gap without extending laterally beyond said periphery of saiddie; and forming a barrier such that, when said lid covers said die,said barrier extends vertically between said lid and said substrate, ispositioned laterally between said outer rim and said die and surroundsand is immediately adjacent to said periphery of said die so as tocontain said thermal compound within said gap, said forming of saidbarrier further comprising: selecting a polymer material; depositingsaid polymer material on said substrate; forming a rigid material onsaid polymer material such that said rigid material is positionedlaterally immediately adjacent to and surrounds said die; and beforesaid covering of said die with said lid, curing said polymer material soas to form said barrier such that said barrier comprises a flexiblecured polymer portion and a rigid portion, said flexible cured polymerportion adhering said rigid portion to said substrate and said selectingsaid depositing and said curing being performed such that said flexiblecured polymer portion of said barrier flexes in response to expansionand contraction of said substrate and said lid during temperaturecycling of said semiconductor module, wherein said lid further has aplurality of extensions mounted on said bottom surface in a patterncorresponding to a pattern of said barrier such that, as said lid coverssaid die, said extensions penetrate said rigid portion so as to fix saidrigid portion to said lid.
 7. The method of claim 6, said extensionscomprising blades.
 8. The method of claim 6, said rigid portioncomprising one of metal and plastic.
 9. The method of claim 6, saidforming of said barrier comprising patterning said barrier with aplurality of discrete sections with openings between said discretesections to allow air and excess thermal compound to escape said barrierinto a space between said barrier and said outer rim during said processof forming said semiconductor module.
 10. The method of claim 6, saidpolymer material comprising a b-stage thermosetting material.
 11. Themethod of claim 6, further comprising forming said lid such that saidlid comprises a pedestal on said corresponding portion of said bottomsurface and adapted to receive said thermal compound.
 12. The method ofclaim 6, further comprising forming said lid such that said lidcomprises vent holes; and after said forming of said semiconductormodule, plugging said vent holes in said lid.
 13. The method of claim 2,said plurality of discrete sections comprising two discrete sections andsaid openings comprising two openings located on opposite sides of saiddie.
 14. The method of claim 2, said plurality of discrete sectionscomprising four discrete sections located adjacent to correspondingsides of said die and said openings comprising four openings located inadjacent to corresponding corners of said die.
 15. The method of claim6, said plurality of discrete sections comprising two discrete sectionsand said openings comprising two openings located on opposite sides ofsaid die.
 16. The method of claim 6, said plurality of discrete sectionscomprising four discrete sections located adjacent to correspondingsides of said die and said openings comprising four openings locatedadjacent to corresponding corners of said die.